Depression is a serious, debilitating disorder that affects millions of people, but treatment research is hampered by the limited reliability of current outcome measures that are often biased by a number of methodological and clinical factors. Such considerations resulted in the issuance of Program Announcement 06-016, "Development of Biomarkers for Mental Health Research and Clinical Utilities" aimed at spurring development of innovative biomarker technologies with clinical utility to assess mental function and dysfunction related to mental illness. The PA identified an "urgent need" for biomarkers as indicators of changes in disorder severity and/or predictors of treatment response that could be effectively applied on an individual basis. Phase I SBIR research successfully established computer-automated assessment of depression severity using fully-structured interactive voice response system interactions with patients and demonstrated feasibility of obtaining valid measures of depression severity and treatment response through vocal acoustic analysis of speech samples obtained over the telephone. As a result of the Phase I pilot study success, Healthcare Technology Systems was successful in persuading an industry sponsor to include vocal acoustic biomarkers as exploratory measures in a methodologically focused randomized clinical trial. This opening creates an opportunity to advance development of vocal acoustic biomarker research faster than would have been possible if Phase II efforts focused solely on technology evaluation in a randomized double-blind placebo controlled trial, as initially envisioned. The Phase II efforts proposed focus on efficient automation of the analytic processes to reduce delivery costs, replication of Phase I results for further validation, generalized extension of the technology for applicability to other patient populations (non-English speakers, children/young adult, and geriatric), and derivation/optimization of multivariate acoustic models to enhance the biomarker sensitivity to treatment response and prediction of the response likelihood for individual patients. The additional data collection, analysis, and presentation of results will be done in collaboration with the Depression Clinical and Research Program at the Massachusetts General Hospital. The product's commercial market is described and a plan for product launch is outlined. Major depression is involved in over 60% of suicides and is a leading cause of disability adjusted life years in the US and worldwide. Development and evaluation of depression treatments in clinical trials is hampered by use of unreliable outcome measures. Establishing a valid, noninvasive, easily obtained, and generalizable biomarker of depression severity and treatment response will contribute to better understanding of depression and development of effective treatments.